Rheostat



(No Model.) 2 Sheets-Sheet 1. E. R. KNOWLES.

RHEOSTAT.

No. 498,799. I Patented June 6,1893.

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in series.

U TED STATES PATENT QFFICE.

EDWARD R. KNOWLES, OF MIDDLETOVVN, CONNECTICUT, ASSIGNOR TO THE SCHUYLERELECTRIC COMPANY, OF CONNECTICUT.

R H EO'STAT.

SPECIFICATION forming part of Letters Patent N 0. 498,799, dated June 6,1893.

Application filed January 9, 1893. fierial No. 457,817- (No model.

new and useful Improvements in Rheostats;

and I do hereby declare the following to be a full, clear, and exactdescription of theinvention, such as will enable others skilled in theart to which it appertains to make and use the same, reference being hadto the accompanying drawings,-and to the letters-of reference markedthereon,which form a part'of this specification.

My invention relates to rheostats, and its object is. to provide acompact and easily regulated apparatus, designed more especially for usewith constant potential electric lamps.

The invention consists in a plurality of cylinders of slate or othernon-conducting, heatresisting material, each having a coil of Wirewrapped around it, the coils being connected One or more movable contactplates or switches enable more or less of the coils to be shunted, tovary the resistance. These and other details of construction arehereinafter set forth and particularly pointed out in the claims.

In the drawings,-Figure l is a side elevation, showing the cover insection. Fig. 2 is a top plan View, with the cover removed. Fig.

- 3 is a section of a binding screw. Fig. 4 is a cross section of one ofthe cylinders; and Fig. 5 is an elevation partly in section, showing aswitch.

A number of cylinders A, of non-conducting, heat-resisting material,preferably slate,

are grouped together, preferably in a circle,

and are secured at equal distances apart to a metal frame, such as thering B, B, by means of screws a. Each cylinder preferably has an annulargroove a near each end, and a transverse hole a 'termina ting in saidgroove. In the surface of the cylinder between the grooves a is ahelical groove a of small pitch.

7 A helical wire coil C of high resistance, such as German silver wire,is wound in the groove a and its ends are secured by being passedthrough the holes (L The adjacent ends of the several coils areconnected, so that the coils are all in series. The bottom ring B,

has ears Z2, through. which pass screws 1), fastening it to a suitablebase, D, preferably the shelf of a wall bracket, as shown. The bracketcontains a number of holes corresponding with the cylinders A, in orderto give access to the screws 0. in the bottom ring B, and also to assistin ventilating the apparatus.

Near the centerof the bracket, or at any other. convenient points, aretwo holes in which are placed insulating bushings E, preferably of lava.The bushing has a flange e to rest against one surface of the bracket,and a washer e of lava is laid upon theother side of the bracketconcentric with the bushing. A screw F passes through the Washer andbushing, which insulate it from the bracket, into the base of a bindingpost G, provided with a set screw g. The terminals insulatingbushings'd, preferably of fiber, in-

serted in holes in the base D, and are each carried to the nearestbinding post, and securely clamped between the base of said post and theflange of the bushing E.

In ordervto enable a portion of the coils to be cut out, one or moremovable switches or bridges are provided, each composed of two metallicpieces H, H, provided with oppositely arranged arms h, h curved toconform to 'the surfaces of the coils. A clamping screw I passes,through a hole in the piece H and is tapped into the piece H. By backingout the screw, the bridge is loosened and may be slipped up or downalong the coils to vary the efiective length of the same, and therebyvary the resistance of the rheostat. The coils are protected by aremovable sheet metal cover K, which rests upon the base D,'and may befastened byascrew-bolt 7c tapped into a boss at in the center of thebase.

Having thus described my invention, what I claim is- 1. A rheostatcomprising a plurality of insulating, heat-resisting cylinders, ahelical coil of-wire encircling each cylinder, said coils beingconnected in series, and one or more movable bridges to connect adjacentcoils between their ends, substantially as described.

2. A rheostat comprising a plurality of slate cylinders, two rigidframes to which said cylinders are attached attheir ends, helical coilsof wire encircling the cylinders and connected in series, and one ormore movable bridges to connect adjacent coils between their ends,substantially as described.

3. In a rheostat, a slate cylinder for supporting a coil of wire, saidcylinder having near each end a transverse hole terminating in anannular groove, and a helical groove of small pitch encircling thecylinder between the annular grooves, substantially as described.

4. 111a rheostat, comprising parallel coils of wire, a bridge forconnecting two adjacent coils, composed of two metallic pieces havingarms to fit the coils, and a screw for clamping said pieces upon thecoils, substantially as described.

5. In a rheostat, the combination with two 20 parallel coils, of themetallic pieces H H,

having the curved arms h, h, and the screw I passing through the piece Hand tapped into the piece l-I, substantially as described.

6. A rheostat, comprising a plurality of grooved slate cylinders,metallic frames to which said cylinders are attached at their ends, abase to which one of said frames is secured, coils of wire on saidcylinders, connected in series, binding posts secured to the base andconnected with the terminals of the coils, one or more movable bridges,to connect adjacent coils, and a sheet metal cover inclosing the entireapparatus, substantially as described.

In testimony whereof I affix my signature in 35 presence of twowitnesses.

EDWARD R. KNOWLES.

WVitnesses:

MAX LOEWENTHAL, J. A. KENIsToN;

